The diagrams relevant for the process were generated using QGRAF[1]}, a Fortran-based program which automatically generates diagrams at a given loop order, once the Feynman rules have been defined. It gave as output a set of diagrams written in terms of propagators and vertices, with corresponding symmetry factors.
From that expressions we recover the diagrams written in terms of Feynman rules with appropriate substitution rules written using the xAct package.
